1. Field of the Invention
This invention relates to an impact damper and, more specifically, to an energy absorbing device having at least two tubes which telescope one into the other and being configured especially for motor vehicles for the dampening of forces on a vehicle which crashes into an obstacle. In the inner space or interior of the impact damper, there may be included at least one dampening fluid which is filled through a filling device; a throttling point; and at least one component which confines the at least one dampening fluid in the inner space.
2. Description of the Prior Art
Energy absorbing devices of this general type have been disclosed, for example: German patent Nos. 22 29 954, and 22 18 952 and German Laid Open patent appln. No. 34 19 165. In such devices of the prior art, two telescoping tubes were employed to include at least one fluid chamber which was filled with a dampening fluid and/or a ga cushion of high pressure design to be contained in a gas chamber. With these types of energy absorbing devices, it has been found that, with an additional heating of the gases and/or the liquid, the energy absorbing devices would explode from heat expansion. The explosion can be caused by the fact that the metallic components and the metallic safety elements may be made of steel, which softens or melts, so that they either no longer provide their safety function or cause the tubes to become useless through bursting or ripping. During the uncontrolled expansion, the bumpers and a portion of the energy absorbing devices to which they are fastened can be thrown together from the vehicle. This type of accident is possible if a particular vehicle or a stock pile of vehicles catches fire. In practice, it has been found that the seals, such as O-rings, which are made from rubber do not burn, but may decompose at 560.degree. C. and turn into ash at 850.degree. C. The steel components would have ceased to properly function at a lower temperature. On the other hand, some plastic components, such as pistons or seals, have been made of particular plastic material which becomes doughy or more pliable at 270.degree. C. and, therefore, seal better than in their original condition, at normal, lower operating temperatures.
It is disadvantageous, therefore, that, in such a dangerous situation, the prior art devices include no opening through which the liquid or the gas could respectively escape. As a result, there can occur a destruction of the metallic components. The energy absorbing device or the components of the energy absorbing device are respectively capable of exploding because of the resulting high internal pressure above 200.degree. C.
Furthermore, safety valves, such as fusible links for the pressure containers, are shown, for example, in German Utility Model No. 75 21 957.7 and German Patent Publication Published for Opposition Purposes No. 27 44 898. With such valves, the pressurized system will experience a fast pressure drop during elevated temperatures. Such devices include separate arrangements for providing flow routes to the pressure container which ar closed off either by means of a soldered in plug or by means of a soldered plug which is installed with a nipple. These devices include the disadvantage of requiring additional components which have no relationship to the actual function or operation of the pressure system. Such additional components are not only costly but, because of the compact structure of such energy absorbing systems for a motor vehicle, are hard to install.